The present invention relates to a stator and an electric motor and more particularly to a stator and an electric motor having a structure for preventing a contact between transition wirings of stator cores.
Many inner-rotor type electric motors in which a rotor having permanent magnets rotates inside a stator on which electromagnets are disposed radially are used. In those inner rotor type electric motors, each electromagnet includes a stator core which is made from a magnetic material and a coil made up of an electric wire wound round the stator core through an insulator and is provided with its magnetic line of force oriented to the rotor or inwards of the stator. In the electric motors constructed in the way described above, since the rotor resides inside the stator, transition wirings for wiring each coil to each other need to be passed round a periphery of an outer circumference of the stator. Because of this, JP-A-2002-325385 discloses a structure in which transition wirings retaining projections are provided on an outer circumferential portion of a stator, so that transition wirings are passed round outer circumferential sides of the projections so as to wire confronting or mating coils of the same phase to each other.
In the case of a star-connected three-phase alternating current motor being used, however, coils of three systems need to be wired, and this requires transition wirings of three systems to be laid out to pass round the periphery of an outer circumference of a stator, and all of the transition wirings of three systems at the most are retained on the same projection. In this case, respective transition wirings are brought into contact with each other on the same projection or in the vicinity thereof. In particular, when a transition wiring which goes from the projection to the coil portion intersects a transition wiring which goes to the adjacent projection, it becomes easy for both the transition wirings to be brought into contact with each other. Here, since such transition wirings are normally insulated wirings (for example, enameled wires), although the contact of transition wirings with each other does not cause a problem on the spot, there may be a possibility that the transition wirings are made to rub against each other due to vibration or the like to thereby break the insulations of portions of the transition wirings which are in contact with each other, whereby a conductive state is produced between the portions in question of the transition wirings.